In order to know for which Instagram account your payment has been declined, you need to:
- Sign into pro.iconosquare.com
- Click on the cog icon at the bottom left of the page
- Go to Settings --> Payment
- Check the "Status" column of your plans
The ones you need to update your payment method for are under the "Waiting for Payment Information Update" status.
For those Instagram handles, you need to click on "Edit Payment Information" and enter your new payment information.